Marsh Killifish

Fundulus confluentus

Fundulidae · freshwater and saltwater and brackish water fish

2 minute read · Species guide

Marsh Killifish field guide illustration

About Marsh Killifish

Marsh killifish are fish of sheltered grassy backwaters rather than open beaches.

Natural history

FishBase places them in brackish bays and freshwater habitats along the western Atlantic and northeastern Gulf coast. Their mixed diet includes small fish, insects, crustaceans, worms, mollusks, and plant material. This is a flexible feeding strategy across several kinds of food.

Breeding males become dark green with pearly spotting, sometimes arranged in vertical rows. Females are brownish olive, with darker dots and short narrow bars. Eggs can survive extended periods out of water, an important life-history feature in a fish occupying shallow coastal margins.

Sources: Fundulus confluentus species summary

Guide sources

Research reviewed 2026-10-19.

Diet and feeding

The FishTraits compilation records these diet categories for this species: algae or phytoplankton; aquatic or other vascular plants; detritus or unidentified plant material; invertebrates or larval fish; larger animal prey (a source category covering fish, crayfish, crabs, or frogs). These are broad categories, not a claim that every individual consumes every example in a category.

Reported feeding positions include bottom feeding and surface or water-column feeding. The compilation combines published observations; diets can vary with age, locality, and available food.

Habitat preferences

Reported habitat associations include medium to large rivers, streams and small rivers.

The source records associations with muck, sand, vegetation, organic debris. An association indicates reported use, rather than an exclusive requirement.

The species is classified as tolerant of a broad range of salinities. This flag does not specify a salinity range for aquarium care.

Reproduction and parental care

The compilation reports a representative maturity age of 0.5 years. Its maturity field summarizes mean, median, or modal estimates, usually for females; male estimates can be used when female data are unavailable. It is not a fixed age at which every fish first breeds.

Batch or serial spawning has been reported somewhere in the species’ range. This does not establish the same spawning pattern for every population.

Recorded spawning months are Mar, Apr, May for the source’s reporting region (FL). This is a regional calendar, not a range-wide schedule.

The reproductive-guild classification includes spawning on open substrates without guarding the brood.

Size and recorded longevity

FishTraits reports a maximum total length of 8 centimetres. Some entries use an estimated asymptotic length; this value should not be treated as a certified record catch.

Recorded longevity in the compilation is 1.5 years. Wild observations were preferred, but captive records were accepted where wild records were unavailable, and unspecified records were assumed wild. The value is not a guaranteed wild lifespan or an aquarium life expectancy.

Range

Where it lives

Share of 1,064 GBIF observation records with a state location, across 14 states.
0%
80.9%
Share of 1,064 GBIF observation records with a state location, across 14 states.

Habitat

Water and movement

Water
WoRMS records this species in fresh water, brackish water and the sea.
Migration
Not migratory

Classification

Taxonomy

Kingdom
Animalia
Phylum
Chordata
Superclass
Actinopterygii
Class
Teleostei
Order
Cyprinodontiformes
Genus
Fundulus
Species
Fundulus confluentus
ITIS TSN
165645
WoRMS AphiaID
159294
GBIF key
5203624

Common questions about Marsh Killifish

What is the scientific name of Marsh Killifish?
The scientific name is Fundulus confluentus, in the family Fundulidae. Classification follows ITIS.
Does Marsh Killifish live in fresh water or salt water?
WoRMS records this species in fresh water, brackish water and the sea.
Where has Marsh Killifish been recorded in the United States?
GBIF has observations in 14 states, with the most records in Florida, North Carolina, Louisiana. The map shows observation records, which do not establish the complete natural range.

Closest relatives

Other Fundulus species

Banded Killifish31 states
Fundulus diaphanusFundulidaeNative and introducedFreshBrackish
Banded Topminnow5 states
Fundulus cingulatusFundulidaeNativeFresh
Barrens Topminnow1 states
Fundulus julisiaFundulidaeNativeFresh
Bayou Killifish6 states
Fundulus pulvereusFundulidaeNativeFreshSaltBrackish
Blackspotted Topminnow17 states
Fundulus olivaceusFundulidaeNativeFresh
Blackstripe Topminnow20 states
Fundulus notatusFundulidaeNativeFresh
Broadstripe Topminnow2 states
Fundulus euryzonusFundulidaeNativeFresh
California Killifish1 states
Fundulus parvipinnisFundulidaeNativeSaltBrackish
Golden Topminnow14 states
Fundulus chrysotusFundulidaeNativeFresh
Gulf Killifish11 states
Fundulus grandisFundulidaeNative and introducedFreshBrackish
Lined Topminnow8 states
Fundulus lineolatusFundulidaeNativeFresh
Longnose Killifish6 states
Fundulus similisFundulidaeNativeSalt
Mummichog22 states
Fundulus heteroclitusFundulidaeNativeFreshSaltBrackish
Northern Starhead Topminnow16 states
Fundulus disparFundulidaeNativeFresh
Northern Studfish21 states
Fundulus catenatusFundulidaeNative and introducedFresh
Plains Killifish16 states
Fundulus zebrinusFundulidaeNative and introducedFreshBrackish
Plains Topminnow11 states
Fundulus sciadicusFundulidaeNative and introducedFresh
Russetfin Topminnow3 states
Fundulus escambiaeFundulidaeNativeFresh
Saltmarsh Topminnow5 states
Fundulus jenkinsiFundulidaeNativeSaltBrackish
Seminole Killifish4 states
Fundulus seminolisFundulidaeNativeFresh
Southern Starhead Topminnow7 states
Fundulus blairaeFundulidaeNativeFresh
Speckled Killifish2 states
Fundulus rathbuniFundulidaeNativeFresh
Spotfin Killifish12 states
Fundulus luciaeFundulidaeNativeSaltBrackish
Stippled Studfish1 states
Fundulus bifaxFundulidaeNativeFresh

Same family

More Fundulidae

Banded Killifish31 states
Fundulus diaphanusFundulidaeNative and introducedFreshBrackish
Banded Topminnow5 states
Fundulus cingulatusFundulidaeNativeFresh
Barrens Topminnow1 states
Fundulus julisiaFundulidaeNativeFresh
Bayou Killifish6 states
Fundulus pulvereusFundulidaeNativeFreshSaltBrackish
Blackspotted Topminnow17 states
Fundulus olivaceusFundulidaeNativeFresh
Blackstripe Topminnow20 states
Fundulus notatusFundulidaeNativeFresh
Blue-fintop Minnow7 states
Lucania goodeiFundulidaeNativeFresh
Broadstripe Topminnow2 states
Fundulus euryzonusFundulidaeNativeFresh
California Killifish1 states
Fundulus parvipinnisFundulidaeNativeSaltBrackish
Diamond Killifish5 states
Adinia xenicaFundulidaeNativeFreshSaltBrackish
Golden Topminnow14 states
Fundulus chrysotusFundulidaeNativeFresh
Gulf Killifish11 states
Fundulus grandisFundulidaeNative and introducedFreshBrackish
Lined Topminnow8 states
Fundulus lineolatusFundulidaeNativeFresh
Longnose Killifish6 states
Fundulus similisFundulidaeNativeSalt
Mummichog22 states
Fundulus heteroclitusFundulidaeNativeFreshSaltBrackish
Northern Starhead Topminnow16 states
Fundulus disparFundulidaeNativeFresh
Northern Studfish21 states
Fundulus catenatusFundulidaeNative and introducedFresh
Plains Killifish16 states
Fundulus zebrinusFundulidaeNative and introducedFreshBrackish
Plains Topminnow11 states
Fundulus sciadicusFundulidaeNative and introducedFresh
Pygmy Killifish5 states
Leptolucania ommataFundulidaeNativeFresh
Rainwater Killifish20 states
Lucania parvaFundulidaeNative and introducedFreshSaltBrackish
Russetfin Topminnow3 states
Fundulus escambiaeFundulidaeNativeFresh
Saltmarsh Topminnow5 states
Fundulus jenkinsiFundulidaeNativeSaltBrackish
Seminole Killifish4 states
Fundulus seminolisFundulidaeNativeFresh

All 32 species in Fundulidae